Process for the selective hydrogenation of fats and fatty acids

ABSTRACT

Fats and fatty acids containing diene, triene or polyene fatty acid residues or containing cis monoene residues are hardened or decolorized by hydrogenating them in the presence of a nickel sub sulfide alone or together with molybdenum and/or tungsten sulfides to form a product having a substantial amount of trans monoene residues.

United States Patent Baltes [54] PROCESS FOR THE SELECTIVE HYDROGENATION OF FATS AND FATTY ACIDS [72] Inventor: Josef Baltes, 2 Hamburg 22,

Hagenau 50, Germany 22 Filed: May 27, 1969 [21] Appl. No.: 828,383

[30] Foreign Application Priority Data June 4, 1968 Germany ..P 17 67 675.4

[52] US. Cl. ..260/409, 99/118 [51] Int. Cl ..Cl1c 3/12 [58] Field of Search ..260/409 [56] References Cited UNITED STATES PATENTS 2,674,634 4/1954 Greensfelder et al. ....260/409 FOREIGN PATENTS OR APPLICATIONS 415,203 8/1934 Great Britain 51 Aug. 29, 1972 OTHER PUBLICATIONS Kirkpatrick Nickel Sulfide Catalysts Advances in Catalysis, Volume II, 1951 Tyutyunnikov et al. Sulfur Containing Nickel as a Catalyst in Hydrogenation of Fat Izv. Vyssh. Ucheb;

Zaved., Pisbeb. Tekhnol. 1968(6), 38- 41. Chem Abst. vol. 70 (1969) 59132t Dierichs et al. Hydrogenation of Crude Montan Wax Chem. Abst. Vol. 55 (1961) 16980e German Pat. 801395 Aluminum catalysts Especially for the Treatment of Hydrocarbon Oils, Chem. Abst. Vol. 45 (1951) 2192b Primary Examiner--Lewis Gotts Assistant Examiner-Catherine L. Mills AttorneyCushman, Darby and Cushman [57] ABSTRACT Fats and fatty acids containing diene, triene or polyene fatty acid residues or containing cis monoene residues are hardened or decolorized by hydrogenating them in the presence of a nickel sub sulfide alone or together with molybdenum and/or tungsten sulfides to form a product having a substantial amount of trans monoene residues.

10 Claims, N0 Drawings PROCESS FOR THE SELECTIVE HYDROGENATION OF FATS AND FATTY ACIDS This invention relates to the hardening and decolorizing of fats (including animal and vegetable oils) and fatty acids by selective hydrogenation. It is known that certain properties of unsaturated fatty acids and their derivatives can be altered by removing a double bond by reaction with hydrogen or by re-arrangement of a double bond structure, with respect either to the steric configuration or the position of a double bond or bonds in the carbon chain of the fatty acid molecule. The first reaction is known as hydrogenation, while the second reaction is tenned isomerization. Unsaturated fatty acids having only one ethylenically unsaturated group, -CH=CH in the chain are known as monoethenoid acids, while fatty acids having two or more such unsaturated groups are known as polyethenoid acids; molecules with two contiguous CH=Cl-l groups, e.g. as the group CH=CH CH =CH are known as conjugated dior polyethenoid acids, while molecules with non-contiguous groups of this configuration are unconjugated dior polyethenoid acids. One spacial type of these unconjugated polyethenoid acids, including naturally occurring linoleic acid and linolenic acid, has an allyl configuration, namely a molecule having at least two such ethylenically unsaturated groups, separated by one CH group only, such as CH=ChCh CH= For reasons of simplicity, and having regard to the nature and special character of the hydrogenation reaction, the term monoene will be used to denote both monoethenoid fatty acids and also polyethenoid fatty acids in which the double bonds form neither a conjugated nor an allyl structure; fatty acids with two conjugated double bonds or a single allyl configuration (as defined above) will be referred to as dienes; compounds having three double bonds in a conjugated or allyl configuration will be referred to as trienes. Molecules having more than three double bonds either in a conjugated configuration or in an allyl configuration will be referred to as polyenes.

It is known that finely divided metallic nickel, preferably deposited on carriers such as kieselguhr, aluminum oxide, silicates and the like, has for a long time been used as a catalyst for hardening fats and fatty acids. While fatty acids are usually completely hydrogenated, in the manufacture of edible fats hardening is partial and selective, so that the degree of unsaturation is usually only lowered to the point that the hardened products, while having melting points in a medium temperature range (44 C.) and possessing certain consistency properties, are free from fatty acid esters with triene and polyene groups. Both the melting oint and the consistency properties also depend on the content of trans-isomers of fatty acid esters in the hardened products. Usually trans-fatty acid residue contents of about 30-40 percent are aimed at, the remaining unsaturated fatty acid residues having the cis-configuration.

The selectivity of the partial hardening depends on the different rates at which different unsaturated fatty acid residues are hydrogenated, and also on the stepwise course followed by the reaction. Trienes and polyenes show the highest reaction speeds, compounds with diene and monoene groups reacting noticeably more slowly. Under the usual conditions the selective hardening takes place stepwise; for example triene groups are first converted to dienes,zthese are then converted to monoenes and the latter are finally converted to saturated groups. According to the simplified reaction scheme trienes K dienes I K, monoenes K saturated products the ratio of the velocity constants can be employed as a measure of the selectivity and can'be calculated from the composition of the particular starting product and hardened products. In addition to the hardening conditions (temperature, hydrogen pressure and stirring) the nature of the catalyst has a significant influence on the degree of selectivity. Theselectivity of nickel catalysts is not high,'butusually suffices for the requirements set in the manufacture of edible fats.

Many attempts have been made to increase the selectivity of the usual nickel catalysts by'modifying their composition. Thus mixed catalysts have become known which contain, besides nickel, other transition metals or alkaline earth metals such as magnesium. Starting from the observation that nickel catalysts which have been repeatedly used show a somewhat better selectivity effect, attempts have also been made to achieve this effect by a partial deactivation of the metallic catalyst, forexample by a slight sulfurization or by reaction with other known contact poisons. All these measures however lead only to moderate success, and artificialdeactivation methods are of questionable value. This is because, as is generally known, nickel catalysts, when used for the hardening of fats, are particularly'sensitive towards contact poisons, and in the presence of such poisons the course of the reaction is significantly interfered with and the hardened products have properties whichdeviate from standard and are undesired. In ad dition to mechanical impurities, phosphatides, soaps and peroxides, the presence of sulfur compounds is particularly feared, since these can under certain circumstances completely inhibit the hydrogenation reaction. For this reason the raw materials intended for hardening are purified asv highly as possible (by treatment with caustic alkali and F ullers earth, washing and drying) in order to remove the contact poisons mentioned and especially sulfur.

Very recently it has become known that copper catalysts and mixed catalysts containing copper show a particularly high selectivity in hardening edible fats. Such catalysts have been used for a long time, inter alia. in the hydrogenation of fatty acid esters to fatty alcohols. Using them it is for example possible to lower the proportion of linolenic acid in soya oil to a large extent, with the formation of the corresponding dieneacid or monoene-acid residues, without significantly reducing the proportion of linoleic acid residues and significantly increasing the proportions of saturated acid and unsaturated trans-fatty acid residues. Hardened products still containing considerable proportions of linoleic acid are obtained in this way, and. areparticularly valuable from the point of view of nutrition physiology and show significantly better stability in use and on storage than the starting material.

[t has now surprisingly been found that fats and fatty acids can be selectively hydrogenated with the aid of nickel subsulfide along or with tunsten sulfide and/or molybdenum sulfide, in such a way that the diene, triene and polyene fatty acid residues are almost completely converted to monoene fatty acid residues of trans-configuration, and that monoene fatty acid residues of cis-configuration originally present undergo a spatial rearrangement to the corresponding transcompounds. Selenides or tellurides of the corresponding transition metals can also be used but do not offer any advantages in respect of selectivity and are more difficult to manufacture.

Accordingly the invention comprises a process for the selective hydrogenation of fats and fatty acids in the presence nickel subsulfide as a catalyst. The catalysts can be used on supports if desired. The sulfides are preferably employed in amounts of 0.05 to parts per 100 parts of fat or fatty acid. (Parts are by weight). It is advantageous to work at a temperature between 100 and 250 C., and using a hydrogen pressure of l to 50 kg/cm.

Examples of suitable sulfides are, molybdenum disulfide, molybdenum pentasulfide, molybdenum sesquisulfide, molybdenum tetrasulfide, molybdenum trisulfide, nickel monosulfide, nickel subsulfide, tungsten disulfide, tungsten trisulfide.

A nickel sub sulfide catalyst for use according to the invention can advantageously be made by mixing an aqueous solution of a nickel salt with a support, such as 'y-aluminum oxide, rendering the mixture weakly alkaline with ammonia, and passing the stoichiometric amount of hydrogen sulfide into the mixture at ordinary or a slightly elevated temperature, whereupon nickel is deposited on the support as the sulfide. After filtration, copious washing, drying and grinding, the material is treated with hydrogen at elevated temperature (for example at 200 C.) and at ordinary or elevated pressure to convert the nickel-sulfur compound completely into Ni S which is then ready to be used as the catalyst. Alternatively the hydrogen treatment can take place in the presence of the material which is to be hydrogenated (as in Examples 2 and 7). Another known method that can be used is to precipitate nickel hydroxide or nickel carbonate from a nickel salt solution, and to convert this, after filtering off and drying, into the sulfide (Ni S by means of hydrogen sulfide or sulfur at elevated temperature.

If a nickel-aluminum alloy is treated with an aqueous sodium sulfide solution and the product copiously washed, nickel sulfide is obtained in the form of a paste which after treatment with hydrogen is also well suited for use as the catalyst. Finally, the sulfidization of known nickel catalysts provides a further useful method of obtaining the desired nickel sulfide catalysts.

Corresponding catalysts and mixed catalysts within the scope of the invention can be made in essentially the same way. The weight ratio of transition metal to sulfur generally corresponds to that of the particular known sulfides (for example Ni S M08; or W8 A particular advantage of the catalysts to be used according to the invention is that they are practically completely insensitive towards contact poisons such as can occur in fats and fatty acids, and that they therefore possess an almost unlimited working life and can be used repeatedly. As a result, less effort can be expended on purifying the fats to be hardened; in general mechanical clarification (filtration with filtration aids), washing and drying suffices.

Hardening, using the catalysts of the invention, can be effected under the usual conditions, in discontinuous or continuous operations. Below C. the hydrogenation takes place very slowly, while temperatures above 250 C. are not necessary and should be avoided in view of possible thermal modification of the starting material. In the case of fats the most favorable temperature range is 180 to 210 C. and in the case of fatty acids 200 to 220 C. The hydrogen pressure can vary within fairly wide limits. Below 1 kg/cm the reaction speed is low, while pressures above 50 kg/cm are not necessary and would therefore be uneconomical. The most advantageous pressure range is usually between 2 and 25 kglcm The hydrogenation up to the final stage, that is to say up to the complete conversion of the polyene fatty acids residues into monoene residues, can be completed in a few hours, the precise time depending on the temperature, hydrogen pressure, and catalyst concentration.

In the case of fats 0.05 to 2 parts of metal sulfide are usually required, and in the case of fatty acids, depending on their nature, 0.5 to 5 parts per 100 parts of fatty material. Higher catalyst concentrations are only appropriate in exceptional cases, and if only for economic reasons concentrations above 10 percent by weight will be normally used. Although hardening will usually be taken to the final stage as indicated above, it is also possible to stop the process at any desired earlier stage.

Fats and fatty acids generally which contain unsatu rated constituents can be treated by the process of the invention, particularly vegetable oils such as soya bean oil, sunflower oil, groundnut oil, rape oil, cottonseed oil, corn oil, oiticica oil, tung oil, perilla oil, grapefruit seed oil, hempseed oil, orangeseed oil, peanut oil, poppyseed oil, safflower oil, sesame seed oil, and the like, and oil from marine animals such as fish oil and whale oil, of which the unsaturated fatty acid residues are known to possess a cis-configuration and which, to the extent that they contain more than one ethylenic group (i.e. are polyethenoid), possess allyl structures. In place of the oils there can be used the corresponding mixtures of the free fatty acids or pure fatty acids such as linoleic acid or linolenic acid. The hardened products obtained have an unusual composition in comparison to the known hardened fats, and as a result possess some novel advantageous properties which are of importance for their use. This is based on the fact that fatty acid residues in which the ethylenic groups have an allyl structure, are hydrogenated to monoene fatty acid residues, but the latter are not at all, or only to a very insignificant extent, converted to saturated fatty acid residues. At the same time a spatial rearrangement of almost all double bonds takes place, so that the unsaturated fatty acid residues remaining in the hardened products possess a trans-configuration. This naturally exerts a significant influence on inter alia their melting behavior. To a minor extent the hydrogenation can be accompanied by a migration of double bonds within the fatty acid chain, whereby fatty acid resides possessing.

are therefore monoenes, and are for practical purposes not hydrogenated under the conditions of the process.

The fats which have been hardened in accordance with the invention are distinguished by high stability towards oxidative influences and have hardly any ten- 5 dency to become rancid either on storage or during use. For this reason they are particularly suitable for baking and deep frying. Their melt behavior over the approximate temperatures range to 40 C., as can be deduced from dilatation measurements, shows their excellent suitability for use as substitutes for cocoa butter, for example for the manufacture of icing fats. Of course the hardened products can also be employed in other cases where solid fats are usually required, for example in the manufacture of margarine.

If the hardening is stopped before the final stage, products are obtained which can contain more or less considerable quantities of liquid constituents at ordinary temperature. These can easily be separated in a known manner, and are distinguished by notable stability towards auto-oxidation, which can be explained by the nature of their double bond systems. The solid products so obtained can be used for the purposes described above.

The hardened fatty acids are mixtures of transmonoene fatty acids and saturated fatty acids, having a content of saturated fatty acid determined by that of the starting material. Technical fatty acids of this nature thus for the first time become accessible in a simple manner. Relative to the comparable solid technical fatty acids, which consist practically completely of saturated fatty acids (palmitic acid, stearic acid and higher acids), they are distinguished by their differing melting behavior (lower melting point and solidification point), while their stability in use and on storage of H.P. Kaufmann, F. Volbert and G. Mankel, FETTE, SEIFEN, ANSTRICHMITTEL, 61, 643-651 (1959); the content of fatty acids having an allyl structure was determined by ultra-violet spectroscopy after isomerization with alkali. The composition of the total fatty acids in the form of their methyl esters was furthermore determined by gas chromatography. The DGF-unit method C-IV-3e (57) served as the basis for all measurements of the melt expansion (dilatation).

, EXAMPLE 1 p 1.5 kg. of de-acidified and bleached soya bean oil (containing 0.06 percent of free fatty acids calculated as oleic acid) and 25 g. of a supported catalyst consisting of 1 part of nickel sulfide (Ni s and 2 parts of 7- aluminum oxide, were introduced into anautoclave of 3 liters capacity fitted with an electromagnetic stirrer and the usual attachments. Thus, 0.55 parts of nickel sulfide (Ni S were used per 100 parts of soya bean oil. After displacingthe air by hydrogen the system was heated to 200 C. with the stirrer running, maintaining a hydrogen pressure of 20 kg/cm Towards the end of the heating-up period hardening commenced, as shown by a reduction in pressure after switching off the hydrogen supply. The hardening was now continued under otherwise identical conditions by re-injecting hydrogen up to a pressure of 20 kg/cm whenever the pressure fell to 15- 16 kglcm Samples were taken from time to time and were used for examination after filtering off the catalyst. After a total of 11 hours the hydrogenation reaction came practically to a stop, no further significant reduction in pressure taking place. The course of the hardening can be seen from the results of the analytical investigations summarized in the Table below.

are similar. TABLE 6 1 D It has also been found that a considerable lightening flydm Iodine Capmary Dim Composition of mm of the color of fats and oils is achieved when the carot1- genation No. melting tation in 7 the total se1 -form noids usually to be found in fats are hydrogenated by P 12 234 in 3? 323; the process of the invention, with the formation of m ,1, bonds colorless constituents. The hydrogenation of the color- 0 132-8 liquid C10 105 0.5 ing constituents takes place preferentially, and this is $3 Cm particularly noticeable in the case of crude palm oil, 45 glB- 0 the red color of which disappears completely after a is: brief period of hydrogenation (up to half an hour), 1% 103.5 26.0 0,, 10.5 though the fat hardening process only just starts 5 3 noticeably in this stage. Thus the invention includes the 1; discoloring of fats and fatty acids without or with con- 50 88.2 32.0 com1tantharden1ng. Cu

The Examples which follow illustrate the invention. C 58.0 The degree of selectivity of the hardening is expressed in percentages in accordance with the main reaction. 5 81.7 34.2 1500 10 50 c,, 10.5 78 so 1350 25/50 c 62.5 Polyene fatty acid Monoene fatty acid 1070 30/50 165.5

l8 monoene fatty acid in] monoene fatty acid in the hardened product the starting product) polyene fatty acid in the starting product In reckoning the selectivity fatty acids which contain two or more double bonds but do not possess an allyl or conjugated structure are counted as monoene fatty acids as explained above. The contents of trans-fatty 5 H acids and double bonds of transconfiguration were determined by infra-red spectroscopy on the methyl esters of the total fatty acids, according to the method =degree of selectivity (in 10/50 c 10.5 so 83 20/50 c, 10.0 25/50 c 68.0 30 50 c 10.5

1.0 10/50 Cl 10.5 as 92 20/50 c 15.5 25/50 C., 72.0 30/50 c 2.0 c,,=

In the column Composition of the Fatty Acids the symbols denote:

C palmitic acid C stearic acid C,, Octadecaene-acid C octadecadiene-acid C, octadecatriene-acid To determine its working life, the catalyst was employed for further experiments and carefully collected after each experiment. After a total of experiments with de-acidified bleached soya oil 22 g. of the catalyst were still available, and were used for a 16th hardening experiment, in which 1.5 kg. of washed, dried and filtered, but not de-acidified and unbleached, soya oil containing 0.42 percent of free fatty acids calculated as oleic acid, were employed. The hardening time in this experiment was only 4 hours. In other respects the conditions described above were followed. The hardened product of this experiment had the following properties and characteristics:

Capillary melting point 33.6 C. Iodine number 80.4

Dilatation in mm /25 g:

1580 at 10/50 C.

1560 at 20/50 C.

1420 at /50 C.

1310 at /50 C.

The total fatty acids consisted of: 10.0% of palmitic acid 8.0% of stearic acid 73.0% octadecaene-acid 8.5% of octadecadiene-acid 0.5% of octadecatriene-acid.

The poly-unsaturated fatty acids of this hardened product, like those of the first-mentioned experiment using an 11 hour hydrogenation time, did not show any allyl structure, that is to say their double bonds were separated from one another by more than one methylene group.

94 percent of the double bonds were in the transform. The degree of selectivity was about 95 percent.

EXAMPLE 2 An autoclave equipped with an electromagnetic stirrer and the usual fittings was charged with 2 kg. of washed, dried and filtered soya bean oil (0.45 percent free fatty acid) and 100 g. of nickel sulfide (NiS) which had been freshly precipitated with exclusion of air and dried, and was flushed with hydrogen and heated to 200 C., after starting the stirrer. During the heating-up period hydrogen was injected up to a pressure of 20 kg/cm and a stream of about 3 liters of hydrogen per minute was then established by means of the appropriate inlet and outlet valves, keeping the pressure in the autoclave constant. Reduction of the sulfide started at once, as shown by the formation of hydrogen sulfide. It was complete after 2 hours, after which the autoclave contents were cooled and filtered, and the filter residue was copiously washed with hexane. After drying in vacuo at 150 C., about 80 g. of a fine dust or powder remained, of composition corresponding to the formula Ni,s,.

1.5 kg. of de-acidified and dried sunflower oil (0.05 percent free fatty acid, iodine number 128.0) were hardened with 30 g. of the above catalyst under the same conditions as in Example 1. The hydrogenation was complete after 6 hours. The hardened product had the following properties and characteristics:

Capillary melting point 35 .2C.

Iodine number 77.3

Dilation in mm"/ 25 g:

1680 at IO/50 C.

1590 at 20/50 C.

1380 at 25/50 C.

1170 at 30/50 C.

The total fatty acids consisted of 6.8% of palmitic acid 8.2% of stearic acid 1.5% of arachidic acid 79.0% of octadecaene-acid 4.5% of octadecadiene-acid.

The latter did not show any allyl structure. 92 percent of the double bonds were in the trans-form. The degree of selectivity was about percent.

EXAMPLE 3 1.5 kg. of de-acidified and dried herring oil (0.06 percent free fatty acid, iodine number 141) were hardened for 5 hours with 30 g. of a nickel sulfide supported catalyst according to Example 1, at 4-5 kg/cm hydrogen pressure, and otherwise under the same conditions as in Example 1. The hardened product had the following properties and characteristics:

Capillary melting point 34.8 C. Iodine number 81.0 Dilatation in mm /25 g: 1530 at 10/50 C. 1500 at 20/50 C. 1410 at 25/50 C. 1290 at 30/50" C. 88 percent of the double bonds were in the transform.

EXAMPLE 4 1.5 kg. of de-acidified and dried Peruvian fish oil (0.06 percent free fatty acid, iodine number 197) were hardened with 30 g. of a commercially available mixed supported catalyst containing 8 percent by weight of nickel sulfide (Ni s and 10 percent by weight of molybdenum sulfide (MoS deposited on 'y-aluminum oxide, in the same way as in Example 1. The initially high speed of hydrogen uptake fell off appreciably after 3 hours, and after a further hour the hydrogenation was stopped.

The hardened product was partly solid and partly liquid at ordinary temperature and had the following properties and characteristics:

Capillary melting point Iodine number Conjugated-unsaturated fatty acids: not detectable Allyl structured unsaturated fatty acids: 1 percent of the total fatty acids.

After standing for several days at C., the liquid part of the hardened product was separated off by means of a pressure filter, leaving about 1 kg. of solid residue. The constituent which is liquid at ordinary temperature had an iodine number of 105, and the solid residue an iodine number of 87.0 and a capillary melting point of 34.8 C.

EXAMPLE 1.5 kg. of commercial distilled soya oil fatty acid were hydrogenated with 45 g. of the supported catalyst specified in Example 1 for 5 hours at 210 C., and 20 kg/cm hydrogen pressure. The properties and characteristics of the starting material and the hardened product are compared below.

bonds The C l8-diene acids found in the hardened product had neither a conjugated nor an allyl double bond system, as proved by ultra-violet spectroscopic measurements in conjunction with alkali isomerization.

EXAMPLE 6 1.5 kg. of crude palm oil (2.3 percent of free fatty acid) were treated with hydrogen with the aid of 30 g. of a mixed supported catalyst consisting of 10 parts of nickel sulfide (M 8 and parts of tungsten sulfide (WS on 75 parts of kieselguhr, at 180 C., and 6 kg/cm pressure, under conditions otherwise identical to those of Example 1. The course of the hardening can be seen from the comparison of the properties and characteristics of the starting oil and hardened products, given below.

l-lydro- Capil- Dilagenation lary Iodine tation Color trans-form of time in melting number mm /25 E at the double bonds minutes po it g. 447 y.

As can be seen, the color of the oil is already considerably lighter after a hydrogenation time of 15 minutes and corresponds to that of an oil which has been heat-bleached in the usual manner, before any significant hardening of the oil has occurred. The

decomposition products produced on heat-bleaching are naturally absent.

What is claimed is:

l. A process for the hardening or decolorizing of a fat or fatty acid containing diene, triene or polyene fatty acid residues or containing cis-monoene residues comprising subjective said fat or fatty acid to hydrogenation conditions in the presence of a catalyst selected from the group consisting of nickel subsulfide and mixtures of nickel subsulfide with at least one of tungsten sulfide and molybdenum sulfide whereby the gie e, trien or polyene re s'dues re selectivel y rogenate to monoene resi ues an almost all 0 the cis-monoene residues present in the starting material or formed during the hydrogenation reaction are isomerized to trans-monoene residues.

2. A process according to claim 1 wherein a mixture of a plurality of the sulfides is employed.

-3. A process according to claim 1 wherein 0.05 to 10 parts by weight of said catalyst is employed per parts by weight of fat or fatty acid.

4. A process according to claim 3 wherein the hydrogenation is carried out at 100 C. to 250 C. at a hydrogen pressure of l to 50 kg/cm.

5. A process according to claim 4 wherein the catalyst consists of nickel sulfide Ni S 6. A process according to claim 1 wherein the catalyst is a mixture of nickel subsulfide with a member of the group consisting of molybdenum sulfide and tungsten sulfide, the catalyst is used in an amount of 0.05 to 10 parts by weight per 100 parts by weight of fat or fatty acid and the hydrogenation is carried out at 100 C. to 250 C. at a hydrogen pressure of 1 to 50 kg/cm*.

7. A precess according to claim 6 wherein the hydrogenation is continued until reaction is substantially complete and a hardened product is obtained.

8. A process according to claim 6 wherein a colored fat is hydrogenated for a time sufficient to decolorize it but insufficient to completely harden it.

9. A process according to claim 1 wherein the catalyst is employed for 16 successive batches of said fat or fatty acid to selectively hydrogenate the fat or fatty acid.

10. A process according to claim 1 wherein the hydrogenation is stopped before there is significant conversion of the monoenes present to saturated fats or fatty acids. 

2. A process according to claim 1 wherein a mixture of a plurality of the sulfides is employed.
 3. A process according to claim 1 wherein 0.05 to 10 parts by weight of said catalyst is employed per 100 parts by weight of fat or fatty acid.
 4. A process according to claim 3 wherein the hydrogenation is carried out at 100* C. to 250* C. at a hydrogen pressure of 1 to 50 kg/cm2.
 5. A process according to claim 4 wherein the catalyst consists of nickel sulfide Ni3S2.
 6. A process according to claim 1 wherein the catalyst is a mixture of nickel subsulfide with a member of the group consisting of molybdenum sulfide and tungsten sulfide, the catalyst is used in an amount of 0.05 to 10 parts by weight per 100 parts by weight of fat or fatty acid and the hydrogenation is carried out at 100* C. to 250* C. at a hydrogen pressure of 1 to 50 kg/cm2.
 7. A precess according to claim 6 wherein the hydrogenation is continued until reaction is substantially complete and a hardened product is obtained.
 8. A process according to claim 6 wherein a colored fat is hydrogenated for a time sufficient to decolorize it but insufficient to completely harden it.
 9. A process according to claim 1 wherein the catalyst is employed for 16 successive batches of said fat or fatty acid to selectively hydrogenate the fat or fatty acid.
 10. A process according to claim 1 wherein the hydrogenation is stopped before there is significant conversion of the monoenes present to saturated fats or fatty acids. 